How calling vb function from js in visual webgui app?

Question

In my Gizmox Webgui application (vb code) I have: "Form1" containing an "HtmlBox1" control In the form I have the following function:

<PermissionSet(SecurityAction.Demand, Name:="FullTrust")> _
<System.Runtime.InteropServices.ComVisibleAttribute(True)> _
Public Sub VbHelloWorld()
MsgBox("Hello Ridha Ammar")
End Sub

In order to call this function from "HtmlBox1.html" I added to the html code of the "HtmlBox1" control the following script:

function showVbFunction (){
window.external.VbHelloWorld ();
}

and the following link:

<a href="#"> Say Hello World From VB </a>

When debugging and clicking the link, I get the following error:

 

"window.external.VbHelloWorld is not a function"

 

The script cannot access the function.

 

Is there anyone who can help me?